MAX8632 19-3623 Rev 1 10/05 Integrated DDR Power-Supply Solution for Desktops, Notebooks, and Graphic Cards General Description Features The MAX8632 integrates a synchronous-buck PWM con- Buck Controller troller to generate V , a sourcing and sinking LDO lin- DDQ Quick-PWM with 100ns Load-Step Response ear regulator to generate VTT, and a 10mA reference Up to 95% Efficiency output buffer to generate VTTR. The buck controller dri- 2V to 28V Input Voltage Range ves two external n-channel MOSFETs to generate output voltages down to 0.7V from a 2V to 28V input with output 1.8V/2.5V Fixed or 0.7V to 5.5V Adjustable Output currents up to 15A. The LDO can sink or source up to Up to 600kHz Selectable Switching Frequency 1.5A continuous and 3A peak current. Both the LDO out- Programmable Current Limit with Foldback put and the 10mA reference buffer output can be made Capability to track the REFIN voltage. These features make the 1.7ms Digital Soft-Start MAX8632 ideally suited for DDR memory applications in Independent Shutdown and Standby Controls desktops, notebooks, and graphic cards. Overvoltage-/Undervoltage-Protection Option The PWM controller in the MAX8632 utilizes Maxims Power-Good Window Comparator proprietary Quick-PWM architecture with programma- LDO Section ble switching frequencies of up to 600kHz. This control Fully Integrated VTT and VTTR Capability scheme handles wide input/output voltage ratios with ease and provides 100ns response to load transients VTT Has 3A Sourcing/Sinking Capability while maintaining high efficiency and a relatively con- Only 20F Ceramic Capacitance Required for VTT stant switching frequency. The MAX8632 offers fully pro- VTT and VTTR Outputs Track V / 2 REFIN grammable UVP/OVP and skip-mode options ideal in All-Ceramic Output-Capacitor Designs portable applications. Skip mode allows for improved 1.0V to 2.8V Input Voltage Range efficiency at lighter loads. Power-Good Window Comparator The VTT and VTTR outputs track to within 1% of V / 2. REFIN The high bandwidth of this LDO regulator allows excel- Ordering Information lent transient response without the need for bulk capac- itors, thus reducing cost and size. PART TEMP RANGE PIN-PACKAGE The buck controller and LDO regulators are provided with MAX8632ETI+ -40C to +85C 28 Thin QFN-EP* 5mm 5mm independent current limits. Adjustable lossless foldback + Denotes lead-free packaging. current limit for the buck regulator is achieved by monitor- * EP = Exposed pad. ing the drain-to-source voltage drop of the low-side MOSFET. Additionally, overvoltage and undervoltage pro- Pin Configuration tection mechanisms are built in. Once the overcurrent condition is removed, the regulator is allowed to enter TOP VIEW soft-start again. This helps minimize power dissipation 21 20 19 18 17 16 15 during a short-circuit condition. The MAX8632 allows flex- V DD 22 14 REFIN ible sequencing and standby power management using the SHDN and STBY inputs, which support all DDR PGND1 13 VTTI 23 operating states. GND 24 12 VTT The MAX8632 is available in a small 5mm 5mm, 28- SKIP 25 11 PGND2 MAX8632 pin thin QFN package. AVDD 26 10 VTTR Applications 9 SHDN 27 VTTS DDR I and DDR II Memory Power Supplies TPO 28 8 SS Desktop Computers 12 34 5 6 7 Notebooks and Desknotes Graphic Cards Game Consoles 5mm x 5mm THIN QFN RAID Networking Typical Operating Circuit appears at end of data sheet. Quick-PWM is a trademark of Maxim Integrated Products, Inc. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLE TON DL OVP/UVP BST REF LX ILIM DH POK1 V IN POK2 OUT STBY FBIntegrated DDR Power-Supply Solution for Desktops, Notebooks, and Graphic Cards ABSOLUTE MAXIMUM RATINGS V to GND .............................................................-0.3V to +30V VTTS to GND............................................-0.3V to (AV + 0.3V) IN DD V AV , VTTI to GND.........................................-0.3V to +6V PGND1, PGND2, TP0 to GND...............................-0.3V to +0.3V DD, DD SHDN, REFIN to GND ..............................................-0.3V to +6V REF Short Circuit to GND...........................................Continuous SS, POK1, POK2, SKIP, ILIM, FB to GND ................-0.3V to +6V Continuous Power Dissipation (T = +70C) A STBY, TON, REF, UVP/OVP to GND ........-0.3V to (AV + 0.3V) 28-Pin 5mm x 5mm Thin QFN (derate 35.7mW/C DD OUT, VTTR to GND ..................................-0.3V to (AV + 0.3V) above +70C).................................................................2.86W DD DL to PGND1..............................................-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40C to +85C DD DH to LX....................................................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C BST LX to BST..................................................................-6V to +0.3V Storage Temperature Range .............................-65C to +150C LX to GND .................................................................-2V to +30V Lead Temperature (soldering, 10s) .................................+300C VTT to GND...............................................-0.3V to (V + 0.3V) VTTI Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = +15V, V = AV = V = STBY = V = V = 5V, V = V = V = 2.5V, UVP/OVP = TP0 = FB = SKIP IN DD DD SHDN BST ILIM OUT REFIN VTTI = GND, PGND1 = PGND2 = LX = GND, TON = OPEN, V = V , T = -40C to +85C, unless otherwise noted. Typical values VTTS VTT A are at T = +25C.) (Note 1) A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS MAIN PWM CONTROLLER V 228 IN Input Voltage Range V V , AV 4.5 5.5 DD DD Output Adjust Range V 0.7 5.5 V OUT FB = OUT 0.693 0.7 0.707 Output Voltage Accuracy FB = GND 2.47 2.5 2.53 V (Note 2) FB = V 1.78 1.8 1.82 DD Soft-Start Ramp Time t Rising edge of SHDN to full current limit 1.7 ms SS TON = GND (600kHz) 170 194 219 V = 15V, IN TON = REF (450kHz) 213 243 273 On-Time t V = 1.5V ns OUT ON TON = open (300kHz) 316 352 389 (Note 3) TON = AV (200kHz) 461 516 571 DD Minimum Off-Time t (Note 3) 200 300 450 ns OFF MIN V Quiescent Supply Current I 25 40 A IN IN V Shutdown Supply Current SHDN = GND 1 5 A IN All on (PWM, VTT, and VTTR on) 2.5 5 AV Quiescent Supply Current I mA DD AVDD STBY = GND (only VTTR and PWM on) 1 2 AV + V Shutdown Supply DD DD SHDN = GND 20 A Current Rising edge of V 4.05 4.25 4.40 V AV Undervoltage-Lockout IN DD Threshold Hysteresis 50 mV V Quiescent Supply Current I Set V = 0.8V 1 5 A DD VDD FB 2 MAX8632